1. Field of the Invention
The present invention relates to a coating liquid, a film production method, a production method of a functional device, a functional device, an organic electroluminescent device, an organic electroluminescent display device, a color filter substrate, a liquid crystal display device, and a wiring substrate, using the coating liquid. More specifically, the present invention relates to a coating liquid preferable for production of a functional film using an ink jet equipment, a film production method, a production method of a functional device, a functional device, an organic electroluminescent device, an organic electroluminescent display device, a color filter substrate, a liquid crystal display device, and a wiring substrate, using the coating liquid.
2. Description of the Related Art
Film-forming techniques have been widely used for production of displays and the like, including formation of semiconductor layers. Particularly, a film-forming technique using an ink jet equipment (ink jet method) has been employed for production of functional films, such as an organic layer of an organic electroluminescent (EL) display device, a color filter layer of a color filter substrate, and a wiring pattern of a metal wiring substrate. According to the ink jet method, the thickness of the film can be easily adjusted, and a photolithography method and the like is not performed, which is different from a film-forming technique of a spin coat method and the like. Therefore, the functional films can be easily produced at low cost.
A coating liquid used in the ink jet method generally contains a functional material and a solvent. In production of functional films by the ink jet method, if the solvent vaporizes at a head part during ejection of the coating liquid and the functional material and the like is deposited, ejection defects such as irregular arrangement on the substrate of the coating liquid or variation in ejection amount are caused. Therefore, selection of the solvent has been an important problem. Particularly in production of current high-definition displays, the amount of the coating liquid ejected from the head part in one ejection is as small as 10 pl or less in production of the functional film. Therefore, the head part is designed to have a small nozzle diameter. Therefore, ejection defects caused by clogging at the head part are easily generated if the solvent vaporizes and the functional material and the like is deposited.
With respect to reduction in the ejection defects, a composition containing a solvent containing at least one heterocyclic compound having one or more substituent groups and containing an oxygen atom as a constituent atom is disclosed as a coating liquid used in a conventional ink jet method. As this heterocyclic compound, particularly compounds containing a furan ring, an oxazole ring and the like, are disclosed (for example, referring to Japanese Kokai Publication No. 2002-371196 (pages 1 to 4). However, these heterocyclic compounds have room for improvement in stability because such compounds easily generate ring-opening by external stimuli such as heat and light, or easily react with the functional material and the like. In addition, difference in drying environment on the substrate after ejection easily causes difference in film thickness between both edges and the central part of the film, and also causes variation in film thickness between the films. Therefore, there is also room for improvement in order to reduce such problems.
With respect to reduction in ejection defects and variation in film thickness, conventionally disclosed is composition of a coating liquid for forming an organic layer, which contains a solvent containing at least one low-volatile liquid solvent having a vapor pressure of 10 mm Hg or less at 20° C. and a boiling point equal to or lower than a transformation temperature of an organic material or a conversion temperature of a precursor, or a composition containing a solvent containing at least one benzene derivative containing one or more substituent group, in which the total number of the carbon in the substituent is 3 or more (for example, referring to Japanese Kokai Publication No. 2001-52861 (pages 1 to 3) and International Publication WO 00/59267 (pages 1 and 39)). In addition, a production method of an organic EL device using an ink composition for organic EL devices, containing a high boiling point solvent with a boiling point of 200° C. or more (for example, referring to Japanese Kokai Publication No. 2003-229256 (pages 1 and 2)).